Method for producing an exhaust gas manifold for a multi-cylinder engine

Abstract

A tube junction is produced having at least two inlets and an outlet, and at least one bend between the two inlets by providing a forging die with a first recess contoured to hold a bent tube piece. A second recess opens into the first recess and, terminates in a moveable counterpunch. A tube piece having two inlets is bent to bring the two inlets into positions relative to each other generally similar to relative positions of the inlets in a finished tube junction. The bent tube piece is placed within the forging die, and pressurized internally to bulge the tube piece wall into the second recess and form a neck for the outlet. Motion of the counterpunch away from the first recess is controlled as the neck forms under pressure in the second recess.

What is claimed is: 
     
       1. A method for producing a tube junction having at least two inlets and an outlet, and at least one bend between said two inlets, comprising the steps: a. providing a forging die with a first recess contoured to hold a bent tube piece, and with a second recess opening into said first recess, said second recess being terminated in a moveable counterpunch;   b. bending a tube piece having two inlets to bring said two inlets into positions relative to each other generally similar to relative positions of said inlets in said tube junction when finished;   c. placing said bent tube piece within said forging die;   d. pressurizing an inside of said bent tube piece to bulge a wall of said tube piece into said second recess to form a neck for said outlet;   e. controlling speed of motion away from said first recess of said counterpunch as said neck forms under pressure in said second recess.   
     
     
       2. A method as in claim 1, further comprising the step; f. applying force proximate at least one said inlet to move material of said tube piece toward said second recess during steps d and e.   
     
     
       3. A method as in claim 2, further comprising the step of: g. removing said pressurization and said forcing of said tube piece when, due to said moving of said at least one inlet, said two inlets are substantially in positions relative to each other as in said tube junction when finished.   
     
     
       4. A method as in claim 1, wherein said speed of motion is controlled by applying a force to said counterpunch that opposes said bulging of said wall. 
     
     
       5. A method as in claim 1, wherein said motion is controlled in relation to pressure in said tube piece. 
     
     
       6. A method as in claim 2, wherein said force proximate said at least one inlet moves said at least one inlet and is controlled in relation to at least one of pressure in said tube piece and distance of inlet movement.